Responding to an appeal to investigate the cancellation of a study of health risks associated with mountaintop removal mining, the U.S. Department of the Interior's Inspector General said the agency was unable to provide "specific criteria" for how it concluded the project should be halted.

In a June 7 letter to Rep. Raul Grijalva, D-Ariz., the DOI's inspector general said the decision to cancel the study being conducted by the National Academies of Science, Engineering and Medicine had been reached without a process the agency could fully explain.

"Other than a general document entitled 'Secretary of the Interior's Priorities', Departmental officials were unable to provide specific criteria, used for their determination whether to allow or cease certain grants and cooperative agreements," the inspector general wrote.

According to department officials, the decision was reached because they felt an analysis would not produce any new information and the costs associated with the study outweighed any potential benefits. However, the inspector general found that the department could not provide sufficient criteria for how they came to this conclusion, adding that it considered the $455,110 already spent on the effort "wasted" as no final product would be produced.

Initially introduced by the Obama administration in 2016, the study was halted in an Aug. 18, 2017, letter from Interior's Office of Surface Mining Reclamation and Enforcement, informing the group that it should "cease all work on a study of the potential health risks for people living near surface coal mine sites in Central Appalachia."

The practice of mountaintop removal is a mining technique that involves using explosives to access coal seams and relocate soil and other materials, often into neighboring valleys.